A common problem experienced by users of telecommunications terminals for audio communication is difficulty in hearing properly a received audio message when the user is listening to the message in a noisy environment. There are many instances where this problem arises, for example at a large railway station, at an airport, in a busy street, in a noisy factory or in a gathering of people, e.g. at a conference. The terminal being used might for example be a mobile telephone or portable radio or it could be a landline telephone handset.
There are ways well known in the prior art of enhancing a signal received by a telecommunications terminal so that the user is better able to hear the communicated audio information, particularly in the presence of background noise. Generally, these involve adaptive and non-adaptive methods of enhancing the gain of the received signal. Where the gain has a maximum setting and is adjusted to reach the maximum setting no further signal enhancement is obtained. Alternatively, if the gain is not limited to a maximum setting, enhancing beyond a particular level will significantly distort the received signal.
Systems are known, e.g. from US 2004/0057586, wherein the spectrum of the received signal is analysed and the signal to noise ratio of components of the spectrum are determined. Components having a low signal to noise ratio are enhanced by an increased gain. This procedure does not however take into account the noise level in the user's environment at the receiving terminal.